Determination of the Adsorption Isotherms of Overpotentially Deposited Hydrogen on a Pt鈭扞r Alloy in H2SO4 Aqueous Solution Using the Phase-Shift Method and Correlation Constants
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- 作者：Jinyoung Chun ; Nam Y. Kim ; Jang H. Chun
- 刊名：Journal of Chemical & Engineering Data
- 出版年：2011
- 出版时间：February 10, 2011
- 年：2011
- 卷：56
- 期：2
- 页码：251-258
- 全文大小：231K
- 年卷期：v.56,no.2(February 10, 2011)
- ISSN：1520-5134
文摘
The phase-shift method and correlation constants, which are unique electrochemical impedance spectroscopy techniques for studying the linear relationship between the phase shift (90掳 鈮?鈭捪?鈮?0掳) versus electric potential (E) behavior for the optimum intermediate frequency and the fractional surface coverage (0 鈮?胃 鈮?1) vs E behavior, are proposed and verified to determine the Frumkin, Langmuir, and Temkin adsorption isotherms and related electrode kinetic and thermodynamic parameters. On a Pt鈭扞r [90:10 % (by weight)] alloy in 0.5 M H2SO4 aqueous solution, the Frumkin and Temkin adsorption isotherms (胃 vs E), equilibrium constants [K = 3.3 路 10鈭? exp(2.5胃) mol鈭? for the Frumkin and K = 3.3 路 10鈭? exp(鈭?.1胃) mol鈭? for the Temkin adsorption isotherm], interaction parameters (g = 鈭?.5 for the Frumkin and g = 2.1 for the Temkin adsorption isotherm), standard Gibbs energies of adsorption of overpotentially deposited (OPD) H [(25.6 鈮?螖G胃0 鈮?19.4) kJ路mol鈭? for K = 3.3 路 10鈭? exp(2.5胃) mol鈭? and 0 鈮?胃 鈮?1 and (20.9 < 螖G胃0 < 24.0) kJ路mol鈭? for K = 3.3 路 10鈭? exp(鈭?.1胃) mol鈭? and 0.2 < 胃 < 0.8], and rates of change of 螖G胃0 of OPD H with 胃 (r = 鈭?.2 kJ路mol鈭? for g = 鈭?.5 and r = 5.2 kJ路mol鈭? for g = 2.1) have been determined and are compared using the phase-shift method and correlation constants. For 0.2 < 胃 < 0.8, a lateral attractive (g < 0) or repulsive (g > 0) interaction between the adsorbed OPD H species appears. On Pt, Ir, and Pt鈭扞r alloys in 0.5 M H2SO4 aqueous solution, the values of K for the Frumkin adsorption isotherms of OPD H decrease with increasing mass ratio of Ir. Negative values of g for the Frumkin adsorption isotherms of OPD H on the Pt, Ir, and Pt鈭扞r alloys in acidic and alkaline H2O and D2O solutions are experimentally and consistently determined. The duality of the lateral attractive and repulsive interactions is a unique feature of the adsorbed OPD H species on the Pt, Ir, and Pt鈭扞r alloys in acidic and alkaline H2O and D2O solutions.